(a) Technical Field
The present invention relates to thin film transistors, and more particularly, to a thin film transistor array panel and a manufacturing method thereof.
(b) Discussion of the Related Art
Liquid crystal displays (LCDs) are one of the most widely used forms of flat panel displays. An LCD includes a pair of panels provided with field-generating electrodes and a liquid crystal (LC) layer interposed between the two panels. The LCD displays images by applying voltages to the field-generating electrodes to generate an electric field in the LC layer that determines the orientation of LC molecules therein to adjust polarization of incident light.
Among the various forms of LCDs, an LCD having a structure in which field generating electrodes are respectively formed on two display panels is widely used. The two display panels include a thin film transistor array panel and a common electrode panel. A plurality of pixel electrodes and thin film transistors are arranged in a matrix format on the thin film transistor array panel. Color filters of red, green, and blue and a light blocking member are formed on the common electrode panel and one common electrode covers the entire surface of the common electrode panel.
In such a liquid crystal display, the pixel electrodes and the color filters are disposed on different display panels such that it may be difficult to properly align the two display panels with each other, thereby potentially generating an alignment error.
A color filter on array (COA) structure in which the pixel electrodes and the color filters are formed on the same display panel may be provided to avoid the potential problem of having to align multiple display panels. In this structure, a light blocking member and the color filter are formed on the same display panel as the pixel electrode.
After forming the color filter on the display panel on which the pixel electrode will be formed, an organic layer having a predetermined thickness is formed to prevent particles of the color filter from diffusing into the pixel electrode or the liquid crystal layer. Then the pixel electrode and the light blocking member are formed on the organic layer. Here, the surface of the light blocking member is higher than the other layers such that the light blocking member may protrude upward. In this case, the cell gap of the liquid crystal display is non-uniform and the average cell gap is reduced. Also, when the organic layer formed on the color filter is relatively thin, the material of the organic layer coated at the edge of the color filter tends to diffuse into a neighboring region because of the steep step shape between the color filter and the other layers make it difficult to cover the edge of the color filters with the organic layer. Additionally, when the organic layer is relatively thick, a portion of the organic layer that would otherwise be removed may remain when forming the contact hole such that the contact characteristic of the contact hole may be reduced. Reduction of the contact characteristic may be expressed as a partial or complete obstruction of the contact hole by excess material of the organic layer that interferes with electrical conduction between conductive lines that are connected therethrough.